Compounds and methods for treating tight junction permeability

ABSTRACT

The present invention provides Larazotide derivative compositions that resist protease degradation, and in various embodiments, do not demonstrate an inverse dose response, and/or can be delivered at higher doses without loss of potency or efficacy, thereby allowing improved therapy more desirable dosing schedules.

FIELD OF THE INVENTION

The present invention provides compositions and methods for treatingconditions associated with a lack of tight junction integrity, includingof the intestinal epithelium.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. Application No.16/971,739 (now U.S. Pat. No. 11,608,359), filed Aug. 21, 2020, which isa National Stage Entry of PCT/US2019/019350, filed Feb. 25, 2019, whichclaims priority to U.S. Provisional Application No. 62/634,536, filed onFeb. 23, 2018, the contents of which are hereby incorporated in theirentirety.

DESCRIPTION OF THE TEXT FILE SUBMITTED ELECTRONICALLY

This application contains a Sequence Listing in XML format submittedelectronically herewith via Patent Center. The contents of the XML copy,created on Jun. 14, 2023, is named “NMT-018C1_116031-5018.xml” and is40,644 bytes in size. The Sequence Listing is incorporated herein byreference in its entirety.

BACKGROUND

The intestinal epithelium is the layer of cells that forms the luminalsurface of the small and large intestines of the gastrointestinal (GI)tract, and represents the largest interface (more than 400 m²) betweenthe external environment and the internal milieu. The intestinalepithelium has two important functions: absorbing nutrients andproviding a barrier against harmful environmental substances such asbacteria, viruses, toxins, and food allergens.

The barrier properties of the intestinal epithelium are regulated byspecialized plasma membrane structures known as tight junctions.Alterations in tight junctions can result in disruptions of theintestinal barrier functions and increased intestinal permeability. Anintact intestinal barrier prevents the permeation of pathogens,antigens, endotoxins, and other proinflammatory substances into thebody, whereas intestinal disintegrity allows their entry, which maytrigger or exacerbate local or systemic inflammatory disease.

Larazotide is a peptide agent that promotes tight junction integrity.Larazotide has the amino acid sequence: Gly Gly Val Leu Val Gln Pro Gly(SEQ ID NO:1), and can be formulated for targeted release in affectedportions of the GI (e.g., small intestine and/or large intestine) ordelivered to other tissues that exhibit reduced integrity of tightjunctions. Larazotide has been described as exhibiting an inverse doseresponse, where higher doses show an attenuated activity or no activityat all. This inverse dose response may limit the overall efficacy of thedrug and requires undesirable dosing schedules.

DESCRIPTION OF THE INVENTION

The present invention provides Larazotide derivative compositions thatresist protease degradation, and in various embodiments, do notdemonstrate an inverse dose response, and/or can be delivered at higherdoses without loss of potency or efficacy, thereby allowing improvedtherapy and/or more desirable dosing schedules.

“Larazotide” is an eight amino acid peptide that has the sequenceGGVLVQPG (SEQ ID NO:1), alternatively depicted using the formulaG1-G2-V3-L4-V5-Q6-P7-G8 to indicate amino acid sequence numbering.Larazotide, when formulated as the salt with acetic acid, is Larazotideacetate. Larazotide functions promotes tight junction integrity,including of the intestinal epithelium, and is being evaluated as atherapy for patients with celiac disease (CeD).

In accordance with certain embodiments, the present invention providesLarazotide derivatives having various amino acid modifications thatconfer increased resistance to exopeptidase degradation, includingaminopeptidase degradation. A protease or peptidase is an enzyme thatcatalyzes the hydrolytic degradation of peptide bonds. Peptidases can beexopeptidases or endopeptidases. An exopeptidase catalyzes the cleavageof the terminal or penultimate peptide bond. Depending on whether theamino acid is released from the amino or the carboxy terminus, anexopeptidase is further characterized as an aminopeptidase or acarboxypeptidase, respectively. An aminopeptidase, such as an enzymefound in the brush border of the small intestine, will cleave one ormore amino acids from the amino terminus of the peptide. Acarboxypeptidase, such as an enzyme present in the digestive pancreaticjuice, will cleave one or more amino acids from the carboxylic end ofthe peptide. A peptide can undergo multiple rounds of N- or C-terminalcleavage.

Larazotide has been shown in clinical trials to exhibit significantbenefit at reducing CeD symptoms, particularly at the lower doses (e.g.,0.5 mg dose). See US 2016/0022760, which is hereby incorporated byreference in its entirety, and in particular for the formulations anddosages outlined therein. Higher doses (e.g., 1 mg and 2 mg doses)showed an attenuation of activity, or no activity at all. In accordancewith this disclosure, it is believed that an aminopeptidase locatedwithin the brush borders of the lumen surface may createLarazotide-derived fragments, including fragments missing N-terminalglycine residues. For example, the fragments GVLVQPG (SEQ ID NO:2) andVLVQPG (SEQ ID NO:3) are inactive as tight junction regulators.Moreover, when these two fragments are mixed with full lengthLarazotide, activity is completely abolished. Local buildup of theseinactive Larazotide fragments (due to excessive doses of Larazotide) mayin fact compete and block function of the peptide. This would explainclinical observations that low doses of Larazotide work best by avoidingthe reservoir of competing inactive fragments.

The present invention provides compounds that promote tight junctionintegrity (e.g., epithelial or endothelial tight junction integrity),and which exhibit resistance to exopeptidases, such as aminopeptidases.In some embodiments, administering the pharmaceutical compositions ofthe present invention to patients in need, avoids substantialaccumulation of inactive peptide fragments such as GVLVQPG (SEQ IDNO:2), VLVQPG (SEQ ID NO:3), VLVQP (SEQ ID NO:4), and GVLVQP (SEQ IDNO:5). In various embodiments, the peptides of the present invention arederivatives of Larazotide with one or more amino acid modifications thatreduce or inhibit exopeptidase activity on the peptide. Thesemodifications include amino acid substitutions at the N- and/or C-terminus to reduce exopeptidase digestion, extension of the N- and/or C-termini to delay exopeptidase digestion of the functional peptide,incorporation of D amino acids, as well as cyclization.

In various embodiments, the peptide comprises the amino acid sequence ofSEQ ID NO: 1, with one or two substitutions (at one or both of the N-and C-termini) of an amino acid having a different side chain, so as toreduce proteolytic susceptibility. In some embodiments, the peptidecomprises amino acid substitutions for one or both of the N-terminalglycine residues, and optionally for the C-terminal Gly, or optionallyfor the two C-terminal amino acid residues. The amino acid substitutionsmay be a genetically-encoded or a non-genetically-encoded amino acid,and which are each optionally D-amino acids.

In various embodiments, the substitutions comprise non-polar aminoacids, and/or amino acids with bulky side chains. Exemplarysubstitutions at the N- and/or C-terminus include amino acids selectedfrom alanine (A), histidine (H), isoleucine (I), leucine (L), methionine(M), phenylalanine (F), proline (P), tryptophan (W), tyrosine (Y), andvaline (V). Non-genetically encoded amino acids include N-methyl aminoacids, allylglycine, selenocysteine, pyrrolysine, N-formylmethionine,β-amino acids such as β-alanine, GABA, δ-Aminolevulinic acid,4-aminobenzoic acid (PABA), 2,4-diaminobutyric acid, α-amino isobutyricacid, 4-aminobutyric acid, 2-amino butyric acid, γ-Abu, ε-Ahx, 6-aminohexanoic acid, 2-amino isobutyric acid, 3-amino propionic acid,omithine, norleucine, norvaline, hydroxyproline, sarcosine, citrulline,homocitrulline, cysteic acid, t-butylglycine, t-butylalanine,phenylglycine, homo-amino acids such as homophenylalanine,cyclohexylalanine, and fluoro-amino acids (such as fluoro-substitutedphenylalanine or tyrosine). In various embodiments, the amino acidsubstitution(s) are selected from alanine, valine, isoleucine, leucine,norleucine, norvaline, and allylgly.

In some embodiments, the peptide comprises a substitution of an aminoacid (e.g., a substitution of one or more N-terminal Gly residues,and/or the C-terminal Gly residue) with a charged side chain. In someembodiments one or both of the N terminal glycine residues are replacedwith an amino acid having a charged side chain. Amino acids withnegatively charged side chains include aspartic acid (D) and glutamicacid (E). Amino acids with positively charged side chains include lysine(K), arginine (R), and histidine (H).

In exemplary embodiments, a methionine (M) replaces one or both of the Nterminal glycine residues of SEQ ID NO: 1.

In some embodiments, the peptide has a single amino acid addition at theN-terminus to prevent or slow aminopeptidase action. While any aminoacid other than Gly could be employed, exemplary peptides in theseembodiments include MGGVLVQPG (SEQ ID NO:6), HGGVLVQPG (SEQ ID NO:7),FGGVLVQPG (SEQ ID NO:8), and LGGVLVQPG (SEQ ID NO:9). Exemplary peptideshave the formula X1-G2-G3-V4-L5-V6-Q7-P8-G9 (SEQ ID NO: 10), where X isa genetically-encoded or non-genetically encoded amino acid other thanGly. In some embodiments, X may be alanine, valine, isoleucine, leucine,norleucine, norvaline, and allylgly, and may optionally be a D-aminoacid.

In various embodiments, the peptide comprises amino acid substitutionsof at least one of the N terminal glycine residues (and the substitutionmay optionally be a D-amino acid), optionally in combination with aC-terminal extension of from 1 to 8 amino acids, such as C-terminalextensions of 2, 3, 4, or 5 amino acids. Some exemplary embodimentsinclude, X1-G2-V3-L4-V5-Q6-P7-G8 (SEQ ID NO:11), G1-X2-V3-L4-V5-Q6-P7-G8(SEQ ID NO:12), X1-X2-V3-L4-V5-Q6-P7-G8 (SEQ ID NO:13),X1-G2-V3-L4-V5-Q6-P7-G8-X9-X10 (SEQ ID NO:14), andX1-X2-V3-L4-V5-Q6-P7-G8-X9-X10 (SEQ ID NO: 15) wherein X is anindependently selected genetically-encoded or non-genetically-encodedamino acid, such as an amino acid selected from A, S, T, W, F, I, L, K,M, C, P, N, Q, E, D, R, H, V, and Y). In some embodiments, theC-terminal extension amino acid(s) comprise one or more Gly residues.

In these or other embodiments, the peptide comprises an addition ofamino acid(s) to the N- and/or C-terminus with respect to the peptide ofSEQ ID NO: 1. The addition of at least one amino acid to the N terminusand/or C-terminus may confer resistance by delaying exopeptidasedegradation because said exopeptidase would have a longer stretch ofamino acids to digest, thus delaying the formation of the inactivefragments.

In various embodiments, the N- and/or C-terminal extension amino acidsmay be selected from non-polar amino acids and/or amino acids with bulkyside chains. Exemplary substitutions at the N- and/or C-terminus includeone or more of Ala, His, Ile, Leu, Met, Phe, Pro, Trp, Tyr, and Val.Non-genetically encoded amino acid useful in these embodiments includeN-methyl amino acids, allylglycine, selenocysteine, pyrrolysine,N-formylmethionine, β-amino acids such as β-alanine, GABA,δ-Aminolevulinic acid, 4-aminobenzoic acid (PABA), 2,4-diaminobutyricacid, α-amino isobutyric acid, 4-aminobutyric acid, 2-amino butyricacid, γ-Abu, ε-Ahx, 6-amino hexanoic acid, 2-amino isobutyric acid,3-amino propionic acid, ornithine, norleucine, norvaline,hydroxyproline, sarcosine, citrulline, homocitrulline, cysteic acid,t-butylglycine, t-butylalanine, phenylglycine, homo-amino acids such ashomophenylalanine, cyclohexylalanine, and fluoro-amino acids (such asfluoro-substituted phenylalanine or tyrosine). In various embodiments,the amino acid substitution(s) are selected from alanine, valine,isoleucine, leucine, norleucine, norvaline, and allylgly.

In various embodiments of the present invention, at least one, at least2, at least 3, at least 4, at least 5, at least 6, at least 7, at least8, at least 9, or at least 10 amino acids are added to the N and/or Cterminus, with respect to SEQ ID NO: 1. In an embodiment, the peptidecomprises the addition of at least one amino acid to both the N and Ctermini with respect to SEQ ID NO: 1, and the additional amino acidresidues are optionally D-amino acids.

In an embodiment, the peptide comprises the addition of at least 2glycine residues to the N or C terminus with respect to SEQ ID NO: 1.For example, the peptide may comprise the formula (GG)^(n)GGVLVQPG,where n=1 to 10 (SEQ ID NO: 16), and where n is optionally 2, 3, 4, or5.

In some aspects, the invention provides the compounds of SEQ ID NO: 1having one or more D-amino acids. D-amino acids are rarely found innature, and exopeptidases, in general, have difficulty recognizingD-amino acids as a substrate. Accordingly, compositions comprising atleast one D-amino acid may provide for the same amino acid sequence butin a left-handed configuration, as opposed to L-amino acids in theright-handed configuration. In various embodiments, peptides of thepresent invention comprising at least one D-amino acid at the N- orC-terminus confer increased resistance to exopeptidase degradation byexopeptidases, and in particular, aminopeptidases. In some embodiments,the peptide exhibits increased resistance to degradation as compared toLarazotide.

In various embodiments, the peptide has at least one, at least two, atleast three, at least four, at least five, at least six, at least seven,or at least eight D-amino acids. In an embodiment, each amino acid ofthe Larazotide derivative (other than Gly) is a D-amino acid, and isoptionally a retro-inverso peptide. A retro-inverso peptide contains theinverse amino acid sequence (e.g., GPQVLVGG, SEQ ID NO:17), with allnon-glycine amino acids present as D-amino acids. Retro-inverso peptidesmaintain side chain topology similar to that of the original L-aminoacid peptide, and render the peptide more resistant to proteolyticdegradation. In some embodiments, the N-terminal Gly of theretro-inverso peptide is substituted with Ala, Leu, Ile, Val, orAllylgly. In these or other embodiments, one or both of the C-terminalGly residues of the retro inverso peptide is/are substituted with anamino acid independently selected from Ala, Leu, Ile, Val, or Allylgly.

In other embodiments, the peptide having the amino acid sequence of SEQID NO: 1 has one or two D-amino acids at the N- and optionally theC-terminus, with all other amino acids in the L configuration. In theseembodiments, the N- and/or C-terminus are substituted or extended suchthat the peptide does not have a glycine at the terminus (Gly does nothave D- and L- configurations). In some embodiments, the terminal Glyresidues are replaced with D-Ala.

D-amino acids are depicted herein using “(d)” to indicate that thefollowing amino acid in the D conformation. Accordingly, exemplarypeptides in accordance with these aspects of the invention include:(d)X1-G2-V3-L4-V5-Q6-P7-G8 (SEQ ID NO:18), G1-G2-V3-L4-V5-Q6-P7-(d)X8(SEQ ID NO:19), (d)X1-(d)X2-V3-L4-V5-Q6-P7-G8 (SEQ ID NO:20),(d)X1-G2-V3-L4-V5-Q6-P7-(d)X8 (SEQ ID NO:21),(d)X1-(d)G2-V3-L4-V5-Q6-P7-(d)X8 (SEQ ID NO:22), and(d)X1-(d)X2-V3-L4-V5-Q6-(d)P7-(d)X8 (SEQ ID NO:23), where X is anindependently selected genetically or non-genetically-encoded amino acidother than Gly. In some embodiments, X is a cyclic side chain for one orboth of the N terminal glycine residues of SEQ ID NO: 1, such asphenylalanine, tyrosine, histidine, proline, or tryptophan.

In these or other embodiments, the peptide is a cyclized derivative ofLarazotide, which can be synthesized using chemical moieties (using wellknown F-moc chemistries, for example) as well as by the incorporation ofamino acid residues with functional groups that allow cyclization, suchas cysteine residues that spontaneously form disulfide bonds to cyclizepeptides or synthetic amino acids that permit covalent cyclization. SeeC. White and A. Yudin, (2011) Nature Chemistry 3: 509-524, the entirecontents of which are hereby incorporated by reference, specificallywith regards to general peptide cyclization method considerations.

Thus, in some embodiments, cyclized Larazotide derivatives aresynthesized to include at least two amino acid modifications so that acovalent linkage, such as a disulfide bond in the case of cysteineresidues, is formed in order to confer increased resistance toexopeptidase degradation, particularly aminopeptidase degradation.

In some embodiments, the peptide is cyclized using reactive groups at ornear the N- and/or C-terminus of the peptide, and using any availablechemistry. In various embodiments, the peptide comprises an amino acidsubstitution or extension on the N-and/or C-terminus having a chemicallyreactive side chain such that a covalent bond (e.g., a disulfide bond inthe case of Cysteines) can be formed, either spontaneously or with theaddition of a chemically reactive reagent (which can be a bivalentreagent in some embodiments, and may contain an alkyl linker structure).The amino acid modifications may comprise insertions or additions ofsaid cysteine residues, or other amino acid having a chemically reactiveside chain, such as a hydroxyl, amine, amide, or sulfhydryl. In otherembodiments, a cyclized Larazotide derivative is formed by introducingat least two synthetic amino acids with side chains that facilitatecovalent linkage. Accordingly, these embodiments can exploit the glycineresidues that will allow the peptide to bend, thus bringing into closeproximity the N- and C-terminal ends, thereby facilitating a covalentlinkage to form.

Specific embodiments include, but are not limited to,G1-G2-C-V3-L4-V5-Q6-P7-G8 (SEQ ID NO:24),(n-1)C-G1-G2-V3-L4-V5-Q6-P7-G8-9C (SEQ ID NO:25) and(n-3)C-(n-2)G-(n-1)G-G1-G2-V3-L4-V5-Q6-P7-G8-9C (SEQ ID NO:26).

In various embodiments, the peptide exhibits increased resistance topeptidase degradation as compared to the peptide of SEQ ID NO: 1. Thedegree of resistance can be quantified using any suitable peptidaseactivity assay. One of skill in the art will appreciate the variousquantitative and qualitative methods in which protein degradation may bemeasured in order to determine susceptibility to peptidase activity. Insome embodiments, the peptide demonstrates resistance to aminopeptidaseactivity, and in some embodiments, a human aminopeptidase found in thebrush borders of the human lumen surface. In some embodiments, thepeptide demonstrates resistance to a carboxypeptidase, such as a humancarboxypeptidase.

In various embodiments, the invention provides methods for promotingtight junction integrity of a tissue, including tight junction integrityof epithelial or endothelial cells, by administering a peptide orcomposition described herein. In some embodiments, the peptide orcomposition is administered to the gastrointestinal tract (GI) toprevent or reduce gastrointestinal inflammation. Compositions can beformulated for targeted release in affected portions of the GI (e.g.,small intestine and/or large intestine). In other embodiments,Larazotide is administered systemically (e.g., intravenously or bysubcutaneous injection). In some embodiments, the peptide composition isadministered to the lungs as a solution aerosol or powder.

In various embodiments, the composition is formulated to have adelayed-release profile, i.e. targeted release of the Larazotidederivatives in the GI tract. The delayed-release profile allows for theLarazotide derivate to not be immediately released upon ingestion; butrather, there is a postponement of the release until the composition islower in the gastrointestinal tract. The derivative can be formulatedfor release in the small intestine (e.g., one or more of duodenum,jejunum, and ileum) and/or the large intestine (e.g., one or more ofcecum, ascending, transverse, descending or sigmoid portions of thecolon, and rectum). In an embodiment, the pharmaceutical composition isformulated to have a delayed-release profile as described in, forexample, U.S. Pat. No. 8,168,594, the entire contents of which arehereby incorporated by reference.

In various embodiments, the compositions of the present invention mayuse one or more modified-release coatings such as delayed-releasecoatings to provide for effective, delayed yet substantial delivery ofthe peptide to the GI tract. For example, a composition can be entericcoated to delay release of the peptide until it reaches the smallintestine or the large intestine.

In some embodiments, the subject has celiac disease, and the peptide isformulated for targeted release in the small intestine, including theduodenum and jejunum (and optionally the ileum). Methods of treatmentwith Larazotide formulations are disclosed US 2016/0022760, which ishereby incorporated by reference in its entirety.

In some embodiments, the invention provides a method for treatingInflammatory Bowel Disease, such as Crohn’s Disease or UlcerativeColitis, by administering the peptides of the present invention,formulated for delivery to affected portions of the GI.

In some embodiments, the invention provides methods of treating otherconditions of the gastrointestinal tract, such as environmentalenteropathy or necrotizing enterocolitis, by administering the peptidesof the present invention formulated for delivery to the GI.

In still other embodiments, the invention provides methods for treatingleaky gut, or methods for improving tight junction integrity of theintestinal epithelium, including in patients having or at risk ofinflammatory liver disease, such as non-alcoholic fatty liver disease(NAFLD), non-alcoholic steatohepatitis (NASH), or a fatty liver diseaseresulting from hepatitis, obesity, diabetes, insulin resistance,hypertriglyceridemia, abetalipoproteinemia, glycogen storage disease,Weber-Christian disease, Wolmans disease, acute fatty liver ofpregnancy, and liver regeneration.

In some embodiments, the subject has chronic kidney disease, which canbe Stage 1, Stage 2, Stage 3, or Stage 4. Kidney disease can manifestfrom small changes in kidney function, resulting in low glomerularfiltration rate (GFR) measured in ml/min/1.73 m², which can eventuallylead to loss of kidney function and/or kidney failure. In someembodiments, patients with Stage 1 chronic kidney disease have a GFR of90 ml/min/1.73 m² or higher, indicating kidney damage with normal kidneyfunction; patients with Stage 2 chronic kidney disease have a GFR of 89to 60 ml/min/1.73 m², indicating kidney damage with mild loss of kidneyfunction; patients with Stage 3a chronic kidney disease have a GFR of 59to 45 ml/min/1.73 m², indicating mild to moderate loss of kidneyfunction; patients with Stage 3b chronic kidney disease have a GFR of 44to 30 ml/min/1.73 m², indicating moderate to severe loss of kidneyfunction; patients with Stage 4 chronic kidney disease have a GFR of 29to 15 ml/min/1.73 m², indicating severe loss of kidney function; andpatients with Stage 5 chronic kidney disease have a GFR of less than 15ml/min/1.73 m², indicating total loss of kidney function and/or kidneyfailure. In further embodiments, patients with chronic kidney diseaseexhibit high levels of serum creatinine.

In some embodiments, the peptide is formulated for pulmonary delivery orsystemic delivery, and administered to subjects having or at risk ofAcute Lung Injury (ALI) or Acute Respiratory Distress Syndrome (ARDS).

In some embodiments, the peptide is administered in unit dosage forms(e.g., tablets, capsules, or solutions), at higher than about 0.5 mg perunit dose, which can provide for improved efficacy as compared to acorresponding unit dose of Larazotide. For example, the peptide unitdose may be about 1 mg or more, or about 2 mg or more, or about 5 mg ormore, or about 10 mg or more. Unit doses may be formulated for sustainedrelease in some embodiments.

In some embodiments, unit doses are administered about 3 times daily.However, in some embodiments, the peptide has a longer half-life in vivothan Larazotide, and thus may have a more durable biological action. Insome embodiments, the peptide composition is administered no more thantwice per day on average, or no more than once per day on average.

Larazotide derivatives of the present invention may be administered inany suitable form, including as a salt. For example, peptides may beadministered as an acetate salt. Alternative salts may be employed,including any pharmaceutically acceptable salt such as those listed inJournal of Pharmaceutical Science, 66, 2-19 (1977) and The Handbook ofPharmaceutical Salts; Properties, Selection, and Use. P. H. Stahl and C.G. Wermuth (eds.), Verlag, Zurich (Switzerland) 2002, which are herebyincorporated by reference in their entirety.

In various embodiments, the peptides are formulated as pharmaceuticalcompositions, which can take the form of tablets, pills, pellets,capsules, capsules containing liquids, capsules containingmultiparticulates, powders, solutions, emulsion, drops, suppositories,emulsions, aerosols, sprays, suspensions, delayed-release formulations,sustained-release formulations, controlled-release formulations, or anyother form suitable for use.

In some embodiments, the pharmaceutical compositions are formulated as acomposition adapted for parenteral administration. Dosage forms suitablefor parenteral administration (e.g. intravenous, intramuscular, orintraperitoneal injection and infusion) include, for example, solutions,suspensions, dispersions, emulsions, and the like. They may also bemanufactured in the form of sterile solid compositions (e.g. lyophilizedcomposition), which can be dissolved or suspended in sterile injectablemedium immediately before use. They may contain, for example, suspendingor dispersing agents.

1. A peptide promoting epithelial and/or endothelial tight junctionintegrity, the peptide comprising the amino acid sequence of SEQ IDNO:1, with one or two amino acid substitutions at the N-terminus, andoptionally one or two amino acid substitutions of the C-terminus.
 2. Thepeptide of claim 1, having one or two amino acid substitutions at theN-terminus and one amino acid substitution at the C-terminus.
 3. Thepeptide of claim 1,wherein the substitution is for a genetically-encodedor a non-genetically-encoded amino acid, and wherein the one or moresubstitutions are optionally D-amino acids.
 4. The peptide of claim 3,wherein the substitutions are for non-polar amino acids.
 5. The peptideof claim 3, wherein the substitution(s) are independently selected fromalanine, valine, isoleucine, leucine, norleucine, norvaline, andallylgly.
 6. The peptide of claim 3, wherein at least one substitutionis for an amino acid having a charged side chain.
 7. The peptide ofclaim 3, wherein a methionine (M) replaces one or both of the N terminalglycine residues of SEQ ID NO:1.
 8. A peptide promoting epithelialand/or endothelial tight junction integrity, the peptide comprising theaddition of one amino acid to the N-terminus of the peptide of SEQ IDNO:1.
 9. The peptide of claim 8, wherein the peptide has the amino acidsequence: MGGVLVQPG (SEQ ID NO:6), HGGVLVQPG (SEQ ID NO:7), FGGVLVQPG(SEQ ID NO:8), and LGGVLVQPG (SEQ ID NO:9).
 10. The peptide of claim 1,wherein the peptide comprises amino acid substitutions of at least oneof the N terminal glycine residue, optionally in combination with aC-terminal extension of from 1 to 8 amino acids.
 11. The peptide ofclaim 10, wherein the peptide has the formula: X1-G2-V3-L4-V5-Q6-P7-G8(SEQ ID NO:11), G1-X2-V3-L4-V5-Q6-P7-G8 (SEQ ID NO:12),X1-X2-V3-L4-V5-Q6-P7-G8 (SEQ ID NO:13), X1-G2-V3-L4-V5-Q6-P7-G8-X9-X10(SEQ ID NO:14), and X1-X2-V3-L4-V5-Q6-P7-G8-X9-X10 (SEQ ID NO:15)wherein X is independently selected from genetically-encoded andnon-genetically-encoded amino acids.
 12. A peptide promoting epithelialand/or endothelial tight junction integrity, the peptide comprising anaddition of amino acid(s) to the N- and/or C-terminus with respect tothe peptide of SEQ ID NO:1.
 13. The peptide of claim 12, wherein the N-and/or C-terminal extension amino acids are selected from non-polaramino acids.
 14. The peptide of claim 13, wherein the N- and/orC-terminal extension amino acids are independently elected from Ala,His, Ile, Leu, Met, Phe, Pro, Trp, Tyr, and Val.
 15. The peptide ofclaim 12, wherein the peptide has the formula (GG)^(n)GGVLVQPG, wheren=1 to 10 (SEQ ID NO: 16).
 16. The peptide of claim 1, wherein thepeptide comprises one or more D-amino acids.
 17. The peptide of claim16, wherein the peptide has one or two D-amino acids at the N-terminusand optionally the C-terminus, with all other non-Gly amino acids in theL configuration.
 18. The peptide of claim 17, wherein the peptide hasthe formula: (d)X1-G2-V3-L4-V5-Q6-P7-G8 (SEQ ID NO:18),G1-G2-V3-L4-V5-Q6-P7-(d)X8 (SEQ ID NO:19), (d)X1-(d)X2-V3-L4-V5-Q6-P7-G8(SEQ ID NO:20), (d)X1-G2-V3-L4-V5-Q6-P7-(d)X8 (SEQ ID NO:21),(d)X1-(d)G2-V3-L4-V5-Q6-P7-(d)X8 (SEQ ID NO:22), and(d)X1-(d)X2-V3-L4-V5-Q6-(d)P7-(d)X8 (SEQ ID NO:23), where X isindependently selected from any genetically or non-genetically-encodedamino acid other than Gly.
 19. The peptide of claim 18, wherein at leastone X is an amino acid with a cyclic side chain, which are optionallyselected from phenylalanine, tyrosine, histidine, proline, ortryptophan.
 20. A cyclic peptide promoting epithelial or endothelialtight junction integrity, the peptide comprising the amino acid sequenceof SEQ ID NO:1, with one or two amino acid substitutions allowing forcyclization.
 21. The cyclic peptide of claim 20, wherein the peptide iscyclized by a disulfide bond between two Cysteine residues.
 22. Thecyclic peptide of claim 21, wherein the peptide has the formulaG1-G2-C-V3-L4-V5-Q6-P7-G8 (SEQ ID NO:24),(n-1)C-G1-G2-V3-L4-V5-Q6-P7-G8-9C (SEQ ID NO:24) and(n-3)C-(n-2)G-(n-1)G-G1-G2-V3-L4-V5-Q6-P7-G8-9C (SEQ ID NO:25). 23-40.(canceled)